CN1884623A

CN1884623A - Purifying method for silver electrolytic solution

Info

Publication number: CN1884623A
Application number: CN 200610031757
Authority: CN
Inventors: 蔡练兵
Original assignee: JINGUI NON-FERROUS METALS Co Ltd CHENZHOU CITY
Current assignee: Chengzhou City Jingui Silver Co Ltd
Priority date: 2006-05-21
Filing date: 2006-05-21
Publication date: 2006-12-27
Anticipated expiration: 2026-05-21
Also published as: CN1884623B

Abstract

This invention is the purification method of silver electrolyte. Heating the silver electrolyte that need to be purified, the Ag can generate aqueous Ag (OH) 2- ions in solution, so most Pb, Cu, Bi, Sb deposit with the form of hydroxides to the bottom of electrolyte and removed. This invention can be applied during electrolyte and refining of Ag, and plays the pivot role in production of qualified silver. There is any agent needed during purification. The electrolyte can be reused.

Description

Method for purifying silver electrolyte

Technical Field

The invention relates to a purification method of electrolyte, in particular to a purification treatment method of silver electrolyte.

Background

Electrolytic refining of metals is well known and widely practiced in practice. For example, the electrolytic refining process of silver is to use the crude silver as anode, titanium plate as cathode and silver nitrate AgNO₃The aqueous solution is used as the electrolyte, and the current is 250-300A/m at the DC voltage of 2-3V²The refining under the conditions of (1) can obtain 99.99% silver, and the pH value of the electrolyte is adjusted by adding acid.

Before electrolysis, the crude silver generally contains a small amount of impurities of various metal components such as lead Pb, copper Cu, bismuth Bi, antimony Sb and the like. In the electrolytic process, the impurities enter the electrolyte, and the impurities are continuously accumulated in the electrolyte to pollute the electrolyte along with the prolonging of the electrolytic operation time. Therefore, efforts are always made to control the contamination of the electrolyte to change its composition, but the chemical composition of the crude silver is complex and cannot be completely and effectively avoided, the contamination level of the electrolyte is increased during the whole use period, and when the impurity content in the electrolyte exceeds a certain level, the electrolyte cannot be used and needs to be replaced. The use of contaminated electrolytes also has the disadvantage that impurities in the electrolyte are absorbed and incorporated into the crystal lattice of the precipitated silver crystals, thereby reducing the quality of the electrolytic silver, for which reason a timely replacement of the contaminated electrolyte is required. The post-treatment of contaminated electrolyte is also cumbersome and costly due to environmental concerns. Therefore, the removal of Pb, Cu, Bi, Sb in the electrolyte during the silver electrorefining process is a difficult problem.

The current common methods are: concentrating and crystallizing the electrolyte for thermal decomposition. Although this method can solve the problem of reuse of purified silver electrolyte, a large amount of dioxide is generated due to thermal decomposition of nitrateNitrogen NO₂The gas pollutes the environment. And the treatment method has the defects of high energy consumption, complex equipment, long purification period, large precious metal loss and the like.

The Chinese patent of invention CN00126155.X also discloses a method for removing bismuth and antimony from silver electrolyte, which utilizes the hydrolysis characteristic of nitrate of bismuth and antimony under low acidity condition, and adds proper amount of silver oxide and ammonia water step by step in the silver electrolyte to filter and recover the bismuth and antimony, and the silver electrolyte can be reused after being adjusted by nitric acid and silver nitrate. The method has the advantages of simple operation, short purification time, reusable electrolyte and low noble metal loss. However, the method can not remove Pb, Cu in the electrolyte at the same time, and the addition of ammonia water can easily generate silver explosion Ag₃N, is also very unsafe for production.

Disclosure of Invention

The invention aims to provide a method for purifying silver electrolyte, which utilizes the hydrolysis characteristic of nitrates of lead Pb, copper Cu, bismuth Bi and antimony Sb in a low-acidity environment to hydrolyze and precipitate the nitrates so as to achieve the aim of removing the lead Pb, the copper Cu, the bismuth B and the antimony Sb.

The purpose of the invention is realized by the following measures:

a process for purifying the silver electrolyte includes such steps as heating the silver electrolyte to be purified, and preparing hydrated ions Ag (OH) from Ag in aqueous solution₂ ^-Adjusting to be purifiedThe pH value of the silver electrolyte is 8-9, and the ion reaction formula in the silver electrolyte is as follows:

at the moment, most Pb, Cu, Bi and Sb in the electrolyte are precipitated at the bottom of the electrolyte in the form of hydroxide; standing for 7-9 hours; filtering the supernatant to obtain the impurities Pb, Cu, Bi,Sb etc. have been reduced to 10^-2Adjusting the electrolyte to acid content of 3-9g/l and silver content of 80-120g/l with nitric acid, and returning to the electrolytic cell for use.

The invention has the following functions and advantages:

the process can be carried out step by step, so that the accumulation of a large amount of impurities in the electrolyte is avoided, the electrolyte even reaches the scrapping degree, a small amount of silver is contained in filter residues in the purification process, and the silver is separated from other impurities by using a proper amount of hydrochloric acid. The process can be carried out partially or completely in practical application, which plays a crucial role in producing qualified electrolytic silver by electrolytic refining of silver. The purification process does not use any medicament. The method has the outstanding advantages that the electrolyte can be recycled, and the method has the unique advantages of simple operation, short purification time, low precious metal loss, strong practicability and the like.

Detailed Description

The invention is illustrated in detail below with specific examples:

example 1

A process for purifying the silver electrolyte includes such steps as heating the silver electrolyte to be purified, and preparing hydrated ions Ag (OH) from Ag in aqueous solution₂ ^-Adjusting the pH of the silver electrolyte to be purified to8 hours later. At the moment, most Pb, Cu, Bi and Sb in the electrolyteare precipitated at the bottom of the electrolyte in the form of hydroxide and are kept stand for 7 hours; filtering the supernatant, wherein the impurities Pb, Cu, Bi, Sb and the like in the supernatant are reduced to 10^-2Adjusting the electrolyte to acid content of 3g/l and silver content of 80g/l with nitric acid, and returning to the electrolytic tank for use.

Example 2

A process for purifying the silver electrolyte includes such steps as heating the silver electrolyte to be purified, adding a small amount of Ag oxide₂O is used as an initiator, and Ag forms hydrated ions in an aqueous solution, namely Ag (OH)₂ ^-And adjusting the pH value of the silver electrolyte to be purified to 9. At this time, most of Pb, Cu, Bi and Sb in the electrolyte,precipitating in the form of hydroxide at the bottom of the electrolyte; standing for 8 hours; filtering the supernatant, wherein the impurities Pb, Cu, Bi, Sb and the like in the supernatant are reduced to 10^-2Adjusting the electrolyte to 6g/l and 100g/l with nitric acid, and returning to the electrolytic tank for use.

Example 3

A process for purifying the silver electrolyte includes such steps as heating the silver electrolyte to be purified, adding a small amount of Ag oxide₂And O is used as an initiator, and the PH value of the silver electrolyte to be purified is adjusted to 8. At the moment, most Pb, Cu, Bi and Sb in the electrolyte are precipitated at the bottom of the electrolyte in the form of hydroxide; standing for 9 hours; filtering the supernatant, wherein the impurities Pb, Cu, Bi, Sb and the like in the supernatant are reduced to 10^-2Adjusting the electrolyte to 9g/l and 120g/l by nitric acid, and then returning the electrolyte to the electrolytic cell for use.

Claims

1. A method for purifying silver electrolyte is characterized by comprising the following steps: heating the silver electrolyte to be purified, forming hydrated ions Ag (OH) by Ag in aqueous solution₂ ^-Adjusting the pH value of the silver electrolyte to be purified to 8-9The ionic reaction occurring in the silver electrolyte is as follows:

at the moment, most Pb, Cu, Bi and Sb in the electrolyte are precipitated at the bottom of the electrolyte in the form of hydroxide; standing for 7-9 hours; filtering the supernatant, wherein the impurities Pb, Cu, Bi, Sb and the like in the supernatant are reduced to 10^-2Adjusting the electrolyte to acid content of 3-9g/l and silver content of 80-120g/l with nitric acid, and returning to the electrolytic cell for use.